Carcinoid tumor metastatic to breast diagnosed by fine needle aspiration. Case report and literature review.

Fine needle aspiration (FNA) biopsy was used to study a mass in the left breast in a patient with a previous history of an ileal carcinoid tumor and later lymph node metastases who presented with bilateral palpable breast masses. The FNA specimens showed the lesion to be a carcinoid tumor. The metastatic nature of the lesion was proven by positive restaining of FNA smears by both the Sevier-Munger technique (demonstrating abundant argyrophilic cytoplasmic granules) and the Fontana-Masson method (showing argentaffin cytoplasmic granules). The distinction between primary and metastatic carcinoid tumors of the breast is discussed, as is their origin and their differentiation from other malignancies of the breast.